1. Field of the Invention
The present invention relates to an information transmitting and receiving system and particularly to a control system for use as remote control, as for example, in television sets.
2. Description of the Prior Art
In remote control systems for television receivers, it has been proposed to transmit control signals which might be ultrasonic or electrical waves having time intervals which differ as a function of the information to be transmitted. These signals are received and detected by counting the time duration of the incoming signals and the television receiver is controlled by the detected signals.
In such prior art remote control systems, the information content is selected to be integral multiples of a unit time interval t.sub.0, as for example, by being t.sub.0, 2t.sub.0, 3t.sub.0, . . . but the following defect exists in such systems.
As shown in FIGS. 1A-1E, which illustrate waveforms used in prior art remote control systems, a unit time interval t.sub.0 is utilized as shown in FIG. 1A where the number of t.sub.0 units is indicative of the intelligence to be transmitted. FIGS. 1B-1E illustrate waveforms having different time lengths corresponding to a different intelligence to be transmitted, respectively. In the four examples, the intelligence illustrated in FIGS. 1B and 1C could be used for increasing and decreasing the volume of the sound of the television set, whereas the information illustrated in FIGS. 1D and 1E could be utilized to change the channels in either a clockwise or counter-clockwise direction, for example. It is to be particularly noted that the length of the signal illustrated in FIG. 1B is exactly twice as long as the length of the signal illustrated in FIG. 1C; and thus, there is a ratio of 2:1 between these two signals and a receiver and detector discrimate and distinguish between signal 1B and signal 1C. However, it is to be noted that signal 1D is 10t.sub.0 in length, whereas the signal 1E is 9t.sub.0 in length. These two signals have a ratio of 10:9. Thus, it is very easy for a receiver and detector to confuse the signals 1D and 1E since their ratio is very close to 1.